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In Thor: Ragnarok Matt Damon plays the role of Actor Loki, but in the cast list his name is not mentioned. The name of Luke Hemsworth who played Actor Thor and Sam Neill who played Actor Odin is mentioned.
This link shows the scene where Matt Damon appeared in the movie dressed as Loki, and Luke Hemsworth is also present playing the role of Thor.
What is the reason for not mentioning Matt Damon's name?